Closes popup.

<div class="definition">
    close()
</div>

<h4>Description</h4>

If a popup is open, it will be closed. If there are currently no open popups, no action will be taken.
This method triggers <span class="argument">onClose</span> event.
<div style="height: 10px"></div>

To close the popup:
<textarea class="javascript">
w2popup.close();
</textarea>
